Per "/lib/libm.so.6 so try adding it to the linker command line" I tried adding -lm to the LIBS line elftosb-10.12.01/makefile.rules, and it now appears to be working.
However, I'm still getting up to speed on LTIB so I did this by diving into /opt/freescale/pkgs/, uncompressing elftosb-10.12.01.tar.gz, making the change, repacking it, and updating elftosb-10.12.01.tar.gz.md5. I thought I should be able to to an scprep followed by an scbuild but ltib would "cowardly refuse" to build elftosb because the directory was already there. Any advice on the "right" way to do this sort of thing would be appreciated.